"We'll make that determination as we go," Harbaugh said. "But there's no rule."

So while Smith appears to be progressing in his comeback from a concussion, the 49ers — the franchise that was once the backdrop for Joe Montana vs. Steve Young — suddenly have a quarterback controversy on their hands, fueled by Harbaugh, rather than the sports talk-show hosts.

This is so premature. The 49ers are built to compete for a Super Bowl run, and Smith's minimal-mistake performance is a key ingredient to that equation.

But Kaepernick, the Nevada product that the 49ers traded up to get in the second round last season, was impressive in his first NFL start on Monday night. He lit up the touted Chicago Bears defense for 243 yards and two touchdowns, with no picks and a 133.1 passer rating in a Monday night rout, following a solid relief effort after Smith was injured against the St. Louis Rams in Week 10.

Having shown flashes this season with his spot role to primarily run Wildcat packages, Kaepernick demonstrated he can flow with the entire offense on Monday night. He wasn't rattled, made the right decisions and put the proper touch on his passes.

Still, Smith has been nobody's slouch in these two seasons under Harbaugh. His current 104.1 passer rating ranks third in the league. Since the start of the 2011 campaign, he has a 35-10 TD-to-INT ratio, including zero picks in two postseason games. The 49ers are 19-5-1 in games that Smith has started for Harbaugh.

But Harbaugh — who got downright testy when I asked him during training camp whether he had to re-establish trust with Smith after flirting with Manning — is seemingly willing to make a switch at the most important position just as the stretch run looms.

"We'll see," he said during his post-game press conference Monday night. "I usually tend to go with the guy who's got the hot hand. And we've got two quarterbacks that have got a hot hand."

That was no slip of the tongue. Harbaugh was asked repeatedly to clarify his stance or backtrack. He was offered the chance to pin it on the injury. He did none of that.

He's true to himself, love it or loathe it.

Harbaugh is refreshing. He embraces living on the edge, and you can see that in the makeup of his team. A former quarterback, you know Harbaugh can relate to Smith on another level, realizing all the pressures, messages and leadership expectations that come with the position.

And he still wants to fuel controversy.

Undoubtedly, Harbaugh isn't worried about soothing Smith's ego. Nor should he be. It takes thick skin, and the No. 1 pick overall in 2005 has that after taking so many lumps and transitioning through one offensive system after another before Harbaugh arrived last year.

This also can't be about any cheap motivational ploy aimed at Smith, Kaepernick or the team at large. Not now. The 49ers culture under Harbaugh already has been established.

So take him at his word? Maybe he's trying to play a mind game with the New Orleans Saints, next on the 49ers' schedule.

If Harbaugh is serious about possibly switching, it seems like such an unnecessary risk. Sure, the stakes are raised. Harbaugh can pick Kaepernick now, then switch back to Smith later. He can flip-flop. But championship history would not be on his side.

The timing seems weird for a controversy, not to mention the circumstance of Smith trying to rebound from the concussion — which had its own controversy, considering how long Harbaugh kept Smith in the game after he took a wicked blow to the head.

The 49ers drafted Kaepernick for a reason. But so much for the inevitable competition or decision playing out over the offseason or in training camp.

That Harbaugh has lit a match to this now tells us one thing for sure. He loves to play with fire.